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If you have 1 driver and give at a certain power, say 100W you will get a certain volume displacement. Add another identical speaker beside it and give it 100W, it will have the same Vd as the other driver for a total of 2Vd, which is +6dB. This is exactly what I put in the example in the first part of my last post.

The equation for sound pressure (in pascals) is

p=U*rho0*f / (2*r)

where U is the volume flow in m3/s
rho0=1.2 kg/m3
f is the frequency in Hz
r is the distance

U is also equal to V*2*pi*f, where V is the volume of air displaced in m3.

To get from sound pressure (p) to sound pressure level (SPL)

SPL = 20*log10(p/pref);

where pref=0.00002 Pa

Double U and you get 6dB.

Quote:

Originally Posted by JerryLove

In which case you are +6db, not +3db.

Yes. In the examples you posted, posts 1 and 2 in the other thread, NathanJ was asking about putting more drivers in the same enclosure. If you add a second driver into the enclosure and give it the same total power as before, you get 3dB more output. Double the total power as I did in my example, and you get 6dB.

Quote:

Originally Posted by JerryLove

Two identical L/R speakers are made of the same material.

Program material.

Quote:

Originally Posted by JerryLove

Who cares about the rest of the program? The rest of the program is unaltered from its original state.

Because when you measure it with an SPL meter, you measure the total, not just the bits you're discussing. I also added in the bit about how non coherent signals add for anyone else who was reading.

Quote:

Originally Posted by JerryLove

Now you do have a single claim in there I don't know to be wrong... that when you separate two sets of drivers playing an identical signal they sum differently than when close together. In short: that I'll hear a different volume from a mono signal sent to two speakers side-by-side and 12' from me than I will with the same speakers and same signal, and same 12' distance, but where they are some arbitrary distance from one another.

What you get in that case is frequency dependent, depending upon the path length differences (time of flight) between the sources and the listener. Ivan gives a very brief explanation in post 5 in the other thread.

Quote:

Originally Posted by JerryLove

Got any references?

Yes. It's basic EE and acoustics. I'd suggest Cordell for amplifiers and Olson and Alton Everest for acoustics as a start.

If you have 1 driver and give at a certain power, say 100W you will get a certain volume displacement. Add another identical speaker beside it and give it 100W, it will have the same Vd as the other driver for a total of 2Vd, which is +6dB. This is exactly what I put in the example in the first part of my last post.

That doesn't disagree with anything I said.

So: to maintain a constant SPL, two drivers must each be -6db relative to a single driver. Which is what I've said.

Quote:

Double U and you get 6dB.

Exactly. So the L and R will have to take 1/4 whatever the center was taking (in power) to match SPL. An increase of 25% power represents <1.5db of gain.

Quote:

Yes. In the examples you posted, posts 1 and 2 in the other thread, NathanJ was asking about putting more drivers in the same enclosure. If you add a second driver into the enclosure and give it the same total power as before, you get 3dB more output. Double the total power as I did in my example, and you get 6dB.

I agree with every bit of that, and I have agreed with every bit of that from the beginning of this thread.

Quote:

Program material.

The program material *is* identical. They are both getting the C-channel material.

Quote:

Because when you measure it with an SPL meter, you measure the total, not just the bits you're discussing. I also added in the bit about how non coherent signals add for anyone else who was reading.
What you get in that case is frequency dependent, depending upon the path length differences (time of flight) between the sources and the listener. Ivan gives a very brief explanation in post 5 in the other thread.

Which has already been dealt with in setting up any competent home theater. The distances *should* be identical to the L and R speaker (within some tolerance), but if not, then one introduces a delay with Audessy or its equivalent to make the arrival time identical. It's already accounted for.

The only thing I've heard thusfar that contradicts any of my description is the thought that, given significant separation, 2 speakers would have to operate -3db rather than -6db to maintain SPL. In which case it is a 50% increase in total power or... just under 1.5db (which is what I've been saying).

You answer the question. I have a speaker 6ft from me. It's putting out a 90db tone (84db at my listening position cause I'm in a really dead room). I turn off that speaker and send the tone to two other identical speakers 6ft from me (one left and one right), how many db does each L and R speaker need to put out for me to hear 84db?

Again: how did you come up with this math? You've started by saying "1 speaker at 0 dB equals 2 speakers at -3 dB"

I was describing the "power law" (aka cosine law) which is the basis for phantom center mixing ratios. If the L speaker is at 0 dB (unity gain, or 1.0), the center is summed with it but at -3 dB (gain = 0.71). 1+0.71 is the summed voltage feeding the L speaker. How much louder is that? 20log(1.71/1) is 4.7 dB.

Please note, the above calculation is to determine the worst case increase in headroom the L amp/speaker need to support for phantom center mode, as that seemed to be an issue of concern a few posts ago. It is not the SPL of the phantom C signal alone.

So I had a bunch of surround setups and in at least some cases (with by most accounts competent, well-matched, well-placed center channel speakers) I found that running in phantom mode improved my sound. Reading the forums, I see that I'm not alone in that experience.

Since there's no cost at all to trying it: I encourage anyone interested in trying for themselves. I suspect that many, though not all, will have positive results.

So I had a bunch of surround setups and in at least some cases (with by most accounts competent, well-matched, well-placed center channel speakers) I found that running in phantom mode improved my sound. Reading the forums, I see that I'm not alone in that experience.

Since there's no cost at all to trying it: I encourage anyone interested in trying for themselves. I suspect that many, though not all, will have positive results.

I completely agree about the testing, it only costs you time. I recently tested it for a bit and it was so much worse than using a center in my case. Went back and am still enjoying my center speaker thoroughly!

Hello. I stumbled across this thread, and for the most part, it's very useful. I Have a living room based 5.1 system comprised of Klipsch WB-14s and a Klipsch WC24 center speaker, a Power Sound Audio XV15 sub and all powered by a Denon X2000. The system is used all day, every day for TV, movies and a lot of music in PL II Music mode. Due to the room itself, I had all three speakers mounted on a shelf just above the TV, and all aimed down and toed in to the MLP. There is only 6' between the L/R with the CC speaker in the middle of course, which is hardly ideal, but still I was happy with the sound.

Last week I was being me and tinkering with the settings and I thought what the hell, let me change center to none......Wow, what a difference for the better. The dialog immediately gained more weight and sounded as though the actor was in my room, instead of a small box like I was used to. The sound stage also dropped and no longer sounded like it is coming from above the TV. In PL II Music mode the image is wider, lower and seems to have more detail. I'm not an audiophile and I can not participate in some of your discussions because I don't have the knowledge. That being said, I'm far from a novice and all my friends & family come to me for HT advice and most importantly, I know what I like.

I sit dead center of the TV 14' away in a 23x16x8 living room that opens to the rest of the house....Your average american house I suppose. My wife sits to my right, and is also the typical american wife in regards to not hearing any difference to anything I do, ever. When I sit in her chair, the image still seems to come from the center of the TV. I figured that without the CC, her spot would be R speaker heavy, but it is not, and even if it was, she wouldn't notice.

I like the result of no CC in my home so much, that I ordered a pair of HTD Level 2 Tower speakers that are going to fit on either side of my 60" TV.......Barely. HTD does offer a Level 2 CC Speaker that is designed to work with the towers I bought, but it is the typical M T M design and it would have to live in my entertainment center, below the TV. All the things that make the typical CC speaker sound bad. So for me, with my speaker placements, in my room the Phantom setting is far superior to a physical CC speaker that was "supposed" to match the rest of my speakers.

Quote:

Originally Posted by Roger Dressler

Let's say the listening volume is comfortably below these limits, as might be the case when people like me listen to movies 15 dB below ref level. Now the amps/speakers will all remain happy regardless of phantom center on/off. In that case, there is no need to worry about electrical overload within the AV processor DSP, DAC, or analog output stages. No need for DRC protection. Just wanted to get that out of the way.

Roger, thanks for your informative posts and I understand, well, some of it. Regarding DRC and the Phantom setting, on my Denon X2000 DRC is still listed as OFF in the surround parameters when listening to any format of DD (2.0/5.1/True HD). If my receiver were going into some kind of DRC when not using a CC speaker, would it do so "silently" and not change the status of the DRC setting, or would it in fact change the setting to ON? I hear no such compression, and the loudest we ever watch our system is -7db, but I am curious of what you think.

Regarding DRC and the Phantom setting, on my Denon X2000 DRC is still listed as OFF in the surround parameters when listening to any format of DD (2.0/5.1/True HD). If my receiver were going into some kind of DRC when not using a CC speaker, would it do so "silently" and not change the status of the DRC setting, or would it in fact change the setting to ON? I hear no such compression, and the loudest we ever watch our system is -7db, but I am curious of what you think.

The display shows you your preference, it does not report what is actually happening. In this case, though, they are the same thing. If you want to confirm, just activate "night mode" or turn DRC on, and you will hear the change.

Yes, amen. If you have a projector system, IMHO the only good time to have a CC speaker is if you can afford an acoustically transparent screen. Even with my relatively small 106" screen, the CC coming from below the screen is quite distracting. My room has a 25" shelf that sets the lower limit on placement, so with all LCR speakers setting on that, they are at ear level, which is good, but with the screen a couple inches above the 8" tall CC and the LR speakers to the side, the dialogue is hard to match with the actors. I can't afford a transparent screen so I just ordered the 120" screen which is the largest I can use, and will not use a CC speaker. The LR speakers will be placed back on their stands to put them vertically in the center [or close to ] of the screen.
Cheers!!!

Quote:

Originally Posted by indio22

With my 100" projector screen, a negative I have found using a center channel, is that the vocals and many other sounds, appear to be coming from below the screen. Well, this is because the center channel is in fact located below the screen! This seems to me a problem intrinsic to single center channel setups - unless perhaps you can place the center channel behind the screen using a material that allows sound to come through.

I tested using the phantom channel setup, and in some cases it seems to do a better job of making sounds appear like they are coming from the charactors/objects on the screen. This is likely because the L/R speakers are located higher up on each side, and volume of the sounds between them can trick the brain into thinking voices and other sounds are coming directly from the screen, or even somewhat left or right on the screen. Center channel can't do this since it is only one speaker.

I would be interested to read comment on the above mechanics, because it does seem a flaw when using a single center channel located below a screen. I would also add, phantom channel to my ear, gives a more expansive sound, compared to center channel, where sometimes if a part of a film has mainly center channel sound, it seems like I am watching the movie in mono sound. Might not be a problem with a small screen, but larger screen it is noticable. On the other hand, a few times using phantom center, the sound did seem too wide and expansive, maybe not focused enough.

For now I am using the real center channel in 5.1 setup, since I have it. But might try playing around with phantom setup again.

I am sure the 277 replies to this thread have beaten the proverbial horse dead but FWIW, I agree with the OP. Took out the center channel in favour of letting the Front LR do more work and couldn't be happier. Bye bye tiny dialogue and welcome dialogue crisp, full and well blended with rest of the audio.

I received my HTD Level Two Towers late Friday night (latest I've ever received a FedEx package) and of course I stayed up late getting them into position, and I ran a quick 1 position Audyssey XT calibration so I could match my sub's gain so the trims would be similar....OCD? Yea, a little The towers are toed into the MLP and they sit 5" on either side of my 60" TV.

I have since ran an 8pt calibration, and all I can say is that HTD won't be receiving any more of my $ for their "matching" M-T-M horizontal Level Two Center speaker. Dialog is as good as I have ever experienced, with weight and clarity. Panning scenes float from right/left & left/right with perfect tonal balance and a perfectly based image in terms of height........... No weird raising or lowering of the image during the panning scene.

When I run my test discs, the pink/white (whatever the correct color is) noise that goes from L/C/R all sounds exactly the same. I have never experienced this before in my room, and I have ALWAYS had a matching center speaker that was designed by the manufacturer to blend with my chosen main speakers. It has never been "mismatched" in terms of being from another manufacturer, and has always been a M-T-M horizontal design. With a center speaker installed the test noise always changed in tone when compared to the L/R speakers, even with Audyssey XT engaged. But it doesn't any more! It sounds exactly like the L/R speakers sound, only in the middle............. That test alone has sold me.

I received my HTD Level Two Towers late Friday night (latest I've ever received a FedEx package) and of course I stayed up late getting them into position, and I ran a quick 1 position Audyssey XT calibration so I could match my sub's gain so the trims would be similar....OCD? Yea, a little The towers are toed into the MLP and they sit 5" on either side of my 60" TV.

I have since ran an 8pt calibration, and all I can say is that HTD won't be receiving any more of my $ for their "matching" M-T-M horizontal Level Two Center speaker. Dialog is as good as I have ever experienced, with weight and clarity. Panning scenes float from right/left & left/right with perfect tonal balance and a perfectly based image in terms of height........... No weird raising or lowering of the image during the panning scene.

When I run my test discs, the pink/white (whatever the correct color is) noise that goes from L/C/R all sounds exactly the same. I have never experienced this before in my room, and I have ALWAYS had a matching center speaker that was designed by the manufacturer to blend with my chosen main speakers. It has never been "mismatched" in terms of being from another manufacturer, and has always been a M-T-M horizontal design. With a center speaker installed the test noise always changed in tone when compared to the L/R speakers, even with Audyssey XT engaged. But it doesn't any more! It sounds exactly like the L/R speakers sound, only in the middle............. That test alone has sold me.

M-T-M horizontal centre speakers are just about the worst imaginable design for a centre speaker. I’d guess that if you compared a phantom centre with a properly designed centre speaker you could feel differently.

Again, one of the problems with a phantom centre is that it is only any use for one listener. Anyone sitting either side of that listener will not get a proper 'centred' centre channel.

M-T-M horizontal centre speakers are just about the worst imaginable design for a centre speaker. I’d guess that if you compared a phantom centre with a properly designed centre speaker you could feel differently.

Again, one of the problems with a phantom centre is that it is only any use for one listener. Anyone sitting either side of that listener will not get a proper 'centred' centre channel.

As you may remember Keith, my system is living room based, so I have to live with certain restrictions on speaker placement and dimensions. I sit 14' away from my display and dead center with it (MLP at its definition) and my wife sits just to the right of me. Our living room is long and rather narrow and the seating is arranged based on this. Tweeter to tweeter is only 68" in terms of separation, and at 14' of distance from the towers, my image is tight just based on placement...... I'm not advocating a phantom setup for everyone, not even close, but for me it's a no brainer.

On a side note, I believe my Klipsch WB14/WC24 speakers and their placement were the source of my Audyssey XT harshness, so expect a detailed post in the appropriate thread in a week or two.

One last thought.............Remember about 25 years ago when most of us on this forum took the "variable audio out" from our TV to our 2-channel stereo amp, and had speakers placed on each side of the TV?? How did we ever do it without a center channel speaker to "anchor" the dialog to the screen? Oh the horror!

M-T-M horizontal centre speakers are just about the worst imaginable design for a centre speaker. I’d guess that if you compared a phantom centre with a properly designed centre speaker you could feel differently.

Again, one of the problems with a phantom centre is that it is only any use for one listener. Anyone sitting either side of that listener will not get a proper 'centred' centre channel.

As you may remember Keith, my system is living room based, so I have to live with certain restrictions on speaker placement and dimensions. I sit 14' away from my display and dead center with it (MLP at its definition) and my wife sits just to the right of me. Our living room is long and rather narrow and the seating is arranged based on this. Tweeter to tweeter is only 68" in terms of separation, and at 14' of distance from the towers, my image is tight just based on placement...... I'm not advocating a phantom setup for everyone, not even close, but for me it's a no brainer.

Yes, it can work for more than one listener in specific circumstances like yours - but most HTs would find it problematic I think. HST, you might still find an even better result if you didn't use an M-T-M speaker for the centre channel.

Quote:

On a side note, I believe my Klipsch WB14/WC24 speakers and their placement were the source of my Audyssey XT harshness, so expect a detailed post in the appropriate thread in a week or two.

Interesting - I will look forward to that. There is no doubt that XT is less beneficial in the HF area than XT32. Combine this with speakers that are perhaps known for being a little bright or forward in that area and there may be a problem as the two factors combine. IRC other Klipsch owners have made similar reports when using XT. I'd be pretty confident that users using XT32 won't have the problem.

EDIT: In case anyone is about to ask why I am so adamant that an M-T-M centre speaker is such a bad idea, here are a few articles that explain it well:

M-T-M horizontal centre speakers are just about the worst imaginable design for a centre speaker. I’d guess that if you compared a phantom centre with a properly designed centre speaker you could feel differently.

Again, one of the problems with a phantom centre is that it is only any use for one listener. Anyone sitting either side of that listener will not get a proper 'centred' centre channel.

I used to hate center channels and was running a phantom center until very recently. I put a "proper" center channel in (not a MTM alignment) and the result beats anything I've gotten in the past. Bye-bye phantom center. Of course, the key was a switch from a TV to a front-projection system—even though my screen is not AT, it was much easier to place the center so it integrates well.

I am sure the 277 replies to this thread have beaten the proverbial horse dead but FWIW, I agree with the OP. Took out the center channel in favour of letting the Front LR do more work and couldn't be happier. Bye bye tiny dialogue and welcome dialogue crisp, full and well blended with rest of the audio.

The main thing IMO is that if someone finds a phantom speaker to give a superior result to a physical centre speaker, it probably points to a problem elsewhere. When Dolby designed 5.1 they knew what they were doing and part of what they were doing involved a physical centre channel. That is how 5.1 is meant to be heard. I have no doubt that some find that a phantom is giving them a better result, but if it were me, I'd try to find out what the real problem is and fix it.

M-T-M horizontal centre speakers are just about the worst imaginable design for a centre speaker. I’d guess that if you compared a phantom centre with a properly designed centre speaker you could feel differently.

Again, one of the problems with a phantom centre is that it is only any use for one listener. Anyone sitting either side of that listener will not get a proper 'centred' centre channel.

I used to hate center channels and was running a phantom center until very recently. I put a "proper" center channel in (not a MTM alignment) and the result beats anything I've gotten in the past. Bye-bye phantom center. Of course, the key was a switch from a TV to a front-projection system—even though my screen is not AT, it was much easier to place the center so it integrates well.

Yes, this was what I was getting at. People using MTM designs will probably have the problems that are associated with that design and they blame the concept of a centre speaker, rather than the particular design of speaker they are using. So they switch to a phantom speaker and find it sounds better than the MTM speaker and leave it at that. The better approach, IMO, is to get to the root cause of the problem not to use a kludge approach, even if the kludge appears to be beneficial.

IME the ideal is three identical speakers across the front. I realise that many find that arrangement difficult to accommodate and if so, I'd recommend they look at purpose designed centre speakers that are not MTM designs.

This is of course my opinion, and have no stats to back it up, but I think there are many more people, not only on this forum, but in real life that use an M-T-M horizontal center speaker due to manufactures marketing and designing that type of speaker to meet the needs of most users who like myself, have living room based systems and a horizontal speaker fits better in most of those cases. Dedicated rooms where a 3rd tower speaker that can be used as a center are definitely in the minority. Whether it's 51% / 49% or 99% / 1% I don't know, but I personally don't have any friends that have a dedicated HT room...............Maybe I need new friends?

This is of course my opinion, and have no stats to back it up, but I think there are many more people, not only on this forum, but in real life that use an M-T-M horizontal center speaker due to manufactures marketing and designing that type of speaker to meet the needs of most users who like myself, have living room based systems and a horizontal speaker fits better in most of those cases. Dedicated rooms where a 3rd tower speaker that can be used as a center are definitely in the minority. Whether it's 51% / 49% or 99% / 1% I don't know, but I personally don't have any friends that have a dedicated HT room...............Maybe I need new friends?

Not all horizontal centre speaker designs are MTM. Just because many people use them doesn't mean they don't have proven design flaws. Have a read of one of the articles I linked to - they explain the problems of MTM designs (when used horizontally as centre speakers) very well.

Not all horizontal centre speaker designs are MTM. Just because many people use them doesn't mean they don't have proven design flaws. Have a read of one of the articles I linked to - they explain the problems of MTM designs (when used horizontally as centre speakers) very well.

I have been reading your links, thanks for posting. What is your opinion on the layout of the HTD Level Two Center speaker? http://www.htd.com/Products/level-two-speakers/Level-TWO-Center-Channel-Speaker# Does placing the tweeter up higher in the cabinet compared to the other drivers alleviate some of the issues with a "conventional" M-T-M? (I realize you haven't heard it, just looking for an opinion)

I just have a two channel with subwoofer set-up. I am mostly interested in good music playback but I also use the system for movies, since my TV in the center of the speakers. The center imaging is just fine for movies and I get a phantom surround affect also. Strange when I can hear sounds from behind and sides and there are no speakers there. I am sure the affect would be better for movies with a full surround set-up, but the phantom affect is good enough for me. I never been that interested in surround sound anyway.

Not all horizontal centre speaker designs are MTM. Just because many people use them doesn't mean they don't have proven design flaws. Have a read of one of the articles I linked to - they explain the problems of MTM designs (when used horizontally as centre speakers) very well.

I have been reading your links, thanks for posting. What is your opinion on the layout of the HTD Level Two Center speaker? http://www.htd.com/Products/level-two-speakers/Level-TWO-Center-Channel-Speaker# Does placing the tweeter up higher in the cabinet compared to the other drivers alleviate some of the issues with a "conventional" M-T-M? (I realize you haven't heard it, just looking for an opinion)

It's above my pay grade really... I am not copping out but I don't want to answer a question I feel unqualified to answer properly. If Bill Fitzmaurice is reading, he will surely be able to comment with far more authority than I can.

HST, my preference would probably be for a centre speaker that also incorporated a mid-range driver as well as a tweeter, between those two woofers. Or, of course, just stand a normal LR speaker up on its end under the screen. If the speaker chosen is only about 24 inches high, most people would have room for that I think. Of course one wouldn't want the centre speaker too close to the floor either or another set of issues arise. It all depends in the end how far people are prepared to go for better sound. If I had a flat panel TV, I'd try to mount it 36 inches from the floor and then use a vertical centre speaker underneath it, separated from the floor by about a foot. That shouldn’t really be all that hard to arrange in many rooms.

I have been reading your links, thanks for posting. What is your opinion on the layout of the HTD Level Two Center speaker? http://www.htd.com/Products/level-two-speakers/Level-TWO-Center-Channel-Speaker# Does placing the tweeter up higher in the cabinet compared to the other drivers alleviate some of the issues with a "conventional" M-T-M? (I realize you haven't heard it, just looking for an opinion)

The closer the midbasses the better, so a layout like that is better than having the tweeter between the midbasses.
There are two issues with horizontal MTMs. One is comb-filtering, which occurs in the frequencies below the crossover to the tweeter where the midbass centers are more than 1 wavelength apart. For instance, with a 3kHz crossover 1 wavelength is 4.5 inches, so combing is almost unavoidable. The other issue is horizontal dispersion of the midbasses where they are close enough to mutually couple (what newbs call 'co-located'). Dispersion is inversely proportional to the width of the source, so an MTM on its side will have less than half the angle of horizontal dispersion than when vertical.

I've read several articles and only have a (consumer-ish) limited understanding of the technical aspects. But what I can say is that after struggling with horizontal centers for a couple of years (my HT listening area is wider than it is deep), the problems with evenness of the front sound stage went away as soon as I started using three identical speakers.

I've read several articles and only have a (consumer-ish) limited understanding of the technical aspects. But what I can say is that after struggling with horizontal centers for a couple of years (my HT listening area is wider than it is deep), the problems with evenness of the front sound stage went away as soon as I started using three identical speakers.

I have used three identical speakers for some time - and three different sets of them too. I agree - it is by far the best arrangement if possible.

Which sounds to me like "You've go a solution that works for you, but in some other solution that I tell you is *better* you will see why I'm right and you don't know what you are talking about: so sell your house immediately (because that's why you couldn't put your L an R 30' apart, and why you can't put an upright in the center in the first place) and buy a new one where the predominant feature is a proper home-theater"

It's just silly. They tried it and they liked the sound. It's not like they've never been to a theater to compare a center channel in a proper setup to have a frame of reference. Why are some people so obsessed with being right that they can't be wrong?